The history of economic development is intimately linked to growth in the use of energy, largely in the form of fossil fuels, with resultant environmental and public health impacts. Many of these impacts have not been evaluated until decades after the damage has been done. Natural gas has been promoted as a cleaner burning fossil fuel with less greenhouse gas emissions. Advances in drilling technologies and the use of hydraulic fracturing allow the exploitation of natural gas in deep deposits of shale. Many US shale regions have been aggressively developed in the last decade. As a result, environmental and health concerns have been expressed regarding surface water, ground water, soil pollution, and air pollution. The speed, magnitude and scale of these activities motivate health studies now, yet almost nothing has been done to address shale development and health. By examining health patterns in relation to location and timing of well activities, we can begin to determine whether there are identifiable health effects associated with any aspect of the industry. The Geisinger Health System is a large integrated health care provider and health plan that is a leader in health care innovation. It provides primary care services to over 400,000 patients in a primary market of over 35 counties in central and northeastern Pennsylvania. It has had an electronic health record (EHR) since 2001, allowing access to longitudinal data on clinical encounters with rich and detailed health information. Its primary market overlaps with the Marcellus region in Pennsylvania. We will build on years of joint experience between Geisinger and Johns Hopkins in using EHR data, clinical outcome measures, geographic information systems (GIS), and the use of secondary data sources for environmental assessment, to examine pregnancy and asthma outcomes in relation to Marcellus shale development. While isolating cause and effect linkages would require more detailed study, we can conduct an efficient and comprehensive evaluation of whether any potential pathways are related to adverse health outcomes. We will study approximately 30,000 Geisinger asthma patients and 22,000 births to mothers with Geisinger prenatal care during the study period 2006-13, proximal to and distant from areas of shale development, with events across the period prior to drilling, during well development, and during natural gas production. We will geocode patient addresses; use GIS and well completion and infrastructure data to derive indices of exposure at the home residence; and then determine whether exposure is associated with pregnancy and asthma outcomes. The proposed research draws on existing data on well development and health, a logical starting point to guide more focused studies of specific pollutant pathways. By evaluating health outcomes in relation to temporal and spatial aspects of well development, all of the many candidate agents and pathways resulting in human exposure are incorporated. Such a study can provide critical information to focus future research, guide policy makers, and ultimately help to protect the health of populations in the region.